1. Field of the Invention
The present invention is directed to a depth of drive control for use with a fastener driving tool, in particular to an adjustable depth of drive control for a fastener driving tool.
2. Description of the Related Art
Portable fastener driving tools for driving staples, nails and other fasteners are widely used for the attachment of substrates. Many fastener driving tools have attempted to control fastener driving depth. Effectively controlling driving depth has been difficult in the past because each fastener is usually driven with the same amount of energy each time that the tool is fired. This has been known to cause fasteners to be driven to an inconsistent depth when there was variation in the density of substrates into which the fasteners are to be driven, for example soft and hard woods. Additionally, it is desirable to be able to consistently select the depth to which the fastener will be driven depending on the application. For some applications it is desirable, for the sake of appearance, to drive the fasteners so they are countersunk below the surface of the substrate. For other applications it may be desirable to have the fastener head flush with the surface of the substrate, and for still other applications, it may be required for the fastener head to stand off from the surface of the substrate.
Several depth of drive controls have been described in the art, such as commonly assigned U.S. Pat. 5,261,587 and 6,012,622, to Robinson and Weinger et al., respectively, the disclosures of which are incorporated herein by reference. Similar fastener driving tools using depth of drive controls are available commercially from ITW-Duo-Fast and ITW-Paslode.
Many of the tools described above have a generally tool-shaped housing with a nosepiece. Depth control has been achieved in fastener driving tools through a tool controlling mechanism, commonly referred to as a drive probe, that is pressed against the surface of the substrate and that is axially movable in relation to the nosepiece in order to adjust the space between the substrate and the housing.
A problem that has been known to occur with many of the tools and depth controls described above is inconsistency in driving depth depending on how much driving and recoiling force is created. For example, many tools are able to alter the amount of driving energy provided, such as by increasing or decreasing the air pressure fed to the tool, which alters the driving depth of the fastener. Also, fastener driving tools, including the drive probe, are known to recoil away from the substrate after firing. Because the drive probe is an integral part of the tool body, the drive probe recoils with the tool body so that the drive probe is moving away from the substrate as the piston is driving the fastener. Tools have also been known to recoil at different speeds so that depth control of the fastener becomes less predictable because the piston is driven to different depths relative to the substrate surface.
Another problem that has occurred is inaccuracy when driving a fastener into a substrate. As a result of the recoil describe above, the drive probe leaves the surface of the substrate when the tool is fired, making a portion of the fastener-driving process unguided. Hence, the fastener may not be driven accurately and straight into the substrate. Another problem has been known to occur when the piston finishes its first drive and contacts a portion of the tool. The driving energy is transferred forward, and an impact mark is left on the surface of the substrate by the tool. This phenomenon is commonly referred to as the xe2x80x9csecond strike.xe2x80x9d
What is needed is a depth of drive control for a fastener driving tool that will effectively, accurately, and consistently control the driving depth of a fastener under various operating conditions while being able to control the second.
In accordance with the present invention, a fastener driving tool having a novel depth of drive control is provided. The fastener driving tool includes a tool body having a cylinder with an axis, wherein the cylinder encloses a piston, and wherein the piston is driven in a driving direction, a depth control probe, and a bumper associated with the depth control probe, the bumper having a trailing surface, wherein the depth control probe is movable with respect to the tool body between an extended position and a retracted position, wherein the depth control probe creates a space having a predetermined length between a surface of a substrate and the trailing surface of the bumper, and wherein a surface of the piston hits the trailing surface of the bumper after the fastener is driven.
Also in accordance with the present invention, a novel fastener driving tool for axially driving a fastener is provided. The fastener driving tool includes a tool body having a cylinder with an axis, the cylinder enclosing a bumper and a piston, wherein the piston is driven in a driving direction, wherein the tool body includes a lifting surface, a depth control probe having a substrate contacting surface and a recoil surface, wherein the depth control probe is movable with respect to the tool body between a retracted position and an extended position, wherein the recoil surface is spaced away from the lifting surface and the substrate contacting surface is in contact with a substrate when the depth control probe is in the retracted position, and wherein the lifting surface is in contact with the recoil surface, the substrate contacting surface is not in contact with the substrate, and the bumper is in contact with the piston when the depth control probe is in the extended position.
Also in accordance with the present invention, a method of controlling the driving depth of a fastener driving tool is provided. The method includes the steps of providing a fastener driving tool having a tool body with an axis, the tool body enclosing a piston, a depth control probe, a bumper associated with the depth control probe, the bumper having a trailing surface, wherein the depth control probe is movable relative to the tool body, and wherein the depth control probe creates a space of a predetermined length between a surface of a substrate and the trailing surface of the bumper, pushing the depth control probe against the surface of the substrate, firing the tool so that the piston is driven in a driving direction, driving a fastener in the driving direction with the piston, hitting the trailing surface of the bumper with the piston so that the piston is no longer moving in the driving direction.